The present invention relates to a laminar staple for corner jointing profiled strips, particularly for manufacturing frames, frameworks and the like.
In the manufacture of borders, frames or similar frameworks made of wood it is known to corner-joint the strips by using laminar staples which are inserted so as to straddle the jointing plane formed by arranging the appropriately chamfered ends of the strips mutually adjacent.
In particular, laminar staples are commercially available which comprise a steel lamina folded so as to form two mutually perpendicular walls and two end ribs or ridges which are perpendicular to the walls and protrude outward, so that the staple assumes a substantially W-shaped profile. Staples of this kind are disclosed in U.S. Pat. Nos. 29,957, 4,681,498 and 5,336,038 and in French patents no. 2,318,715 and 2,525,949.
To mutually joint two profiled strips, cut for example at an angle of 45.degree. in order to be arranged at right angles to each other, said W-shaped staples are inserted so as to straddle the jointing plane formed by arranging the strips mutually adjacent, so that the edge formed by the perpendicular walls and arranged on the centerline plane of the staple lies on the joint. In order to facilitate insertion, one of the edges having a W-shaped profile of the staples is sharp.
In order to make the joint of the strips as invisible as possible, there is a trend to use staples which are as high as possible in relation to the height of the strips. However, using high staples facilitates the onset of cracks in the exposed surface of the strips. It has been observed that the cracks decrease as the angle formed by the ribs with respect to the walls of the staples increases. However, as this angle increases the force with which the strips are mutually fastened decreases, producing a wider and accordingly more visible jointing line.